Year	Percent
1960	5.6372
1961	10.64468
1962	11.21469
1963	10.19443
1964	8.48263
1965	8.67131
1966	8.55956
1967	7.70445
1968	7.2004
1969	6.87344
1970	8.98978
1971	11.36399
1972	11.97963
1973	13.22947
1974	14.91515
1975	13.75593
1976	13.8237
1977	12.86573
1978	10.57187
1979	8.20054
1980	15.72919
1981	19.19481
1982	22.60237
1983	24.25976
1984	29.82335
1985	28.7068
1986	24.51141
1987	27.93073
1988	28.61441
1989	25.58908
1990	23.40182
1991	23.08972
1992	23.72094
1993	24.70837
1994	31.65961
1995	33.83525
1996	36.83747
1997	39.41325
1998	26.43338
1999	26.28493
2000	30.14074
2001	36.32075
2002	36.74608
2003	37.39076
2004	39.70165
2005	37.94252
2006	40.74504
2007	41.03976
2008	43.69687
2009	37.70648
2010	38.79089
2011	45.13368
2012	44.5097
2013	42.444
2014	42.79526
2015	40.83211
2016	39.49743
2017	45.9192